There where some rumors that the Ocean Club and the Tapas 9 were engaged in so called sexual “swinging” practice. This is based on some meta-evidence, so e.g. with some difficulties to explain some strange witnesses statements of or around e.g. Robert Murat, Jez Wilkins and Jane Tanner.
Especially the, from forensics viewpoint, not really compatible and non-convincing statements of Wilkins / Gerry McCann / Tanner regarding the Tanner-Sighting gave reason to some →rumors: So, for what reason non-Tapas witness Wilkins did eventually give a wrong statement in favour of Tapas-members Gerry and Jane?
The McCann's sued British Tabloids over such allegations →in 2008 with the help of their Carter Ruck Lawyers, those who claimed “…From the late summer of 2007 until February 2008, the Defendant newspapers published over one hundred articles which were seriously defamatory of Mr and Mrs McCann. The general theme of the articles was to suggest that Mr and Mrs McCann were responsible for the death of Madeleine or that there were strong or reasonable grounds for so suspecting and that they had then disposed of her body; and that they had then conspired to cover up their actions, including by creating “diversions” to divert the police's attention away from evidence which would expose their guilt. …In addition to the allegations referred to above, the Daily Star published further articles (under the headlines “MADDIE MUM 'SOLD' HER” and “MADDIE 'SOLD' BY HARD-UP MCCANNS”) which sought to allege that Mr and Mrs McCann had sold their daughter in order to ease their financial burdens. A further article alleged that Mr and Mrs McCann were involved in “swinging” or wife-swapping orgies. As the Defendant now acknowledges, all of these allegations were, and remain, entirely untrue….Naturally, the repeated publication of these utterly false and defamatory allegations has caused untold distress to Mr and Mrs McCann. …”
Besides this but the “Swinging” allegation seemingly plays just a minor role in the case, as except to the Tanner-Event, I see no great clues. Definitely Swinging is not a criminal act, and thus should not be in front of any further investigations.
Some more sinister rumors are regarding the role of Philip Martin Edmonds, who was at Praia da Luz in Portugal when Madeleine McCann disappeared. See →Aangirfan “MADELEINE McCANN; THE KRAY TWINS; MARGARET HODGE”